I agree with all of the above! Start with DRESSAGE! But if you can find an event barn, that would be even better. Start getting him used to everything. Take him to a XC course and just canter him around, take him through the water. I have an OTTB that I got 2 years ago as a 3 year old. I didn't start jumping til he was 4 and didnt do anything over 2ft til he was 4 and a half to 5. But I wish I had taken him more places when he was younger. He is great and honest jumper, but it's taken me a while to get him used to to wide, open XC. I think if i'd introduced him to it earlier he'd be a little better right now.
As for the levels, at recognized USEA events the lowest level is beginner novice which is 2'7". But lots of places have schooling shows and the levels vary per show. Around here we have whats called Tadpole. It either all cross rails with little baby verticals or it can be 2'3". It really depends on the place. When you do get ready to start eventing, go watch some schooling shows and see what level you think he could do.
Noticed you live in illinios which is area 4. Take a look at this site USEA Area IV
There's a list of all the trainers, XC schooling places, schooling shows, and recognized shows, and clinics in the area.
Fox hunting as MIeventer said CAN be good, but it can also be very bad. If you do go foxhunting, especially with a young horse you really need to look into the place more. We have two hunts around here. One is a drag hunt and is done on very nice, open trails with great footing. The other is a real hunt and they go FAST and they go through creeks, rocks, bad terrain, whatever they have to do. I went to the second one once and it would NOT be a good place for a green horse, even hilltopping, which I did, was a little ridiculous.